Window regulators for operating a moveable glazing panel between open and closed positions typically have a motor or other drive means for delivering drive force to a gear and linkage assembly. Generally, a quadrant or sector gear is mounted at one end of a lifting arm by welding, riveting or other fixed mounting means. The other end of the lifting arm is connected near the perimeter of the glazing panel. Frequently a cross-arm pivotally connected to the lifting arm at or near respective mid-points is also connected to the glazing panel at one end and is supported in a travel channel at the other end. The components of the window regulator assembly must be sufficiently durable to withstand and transmit the drive forces necessary for opening and closing the window. Drive forces experienced at certain points of travel of the glazing panel are substantially higher than those experienced at other points of travel. Most notably, forces experienced by the window assembly components tend to peak when a drive motor is first actuated, that is, when the motor "torques-up." This occurs when the glazing panel is moved from its full up or full down position, and also when it is moved from any stationary position in between. Similarly, peak forces are experienced by the window regulator assembly components when the glazing panel stalls during travel, such as upon reaching its full up or full down position, or when being stopped due to an intrusion or other blockage of the glazing panel as it travels.
In known window regulator assemblies, all components must be designed and fabricated with sufficient rigidity and durability to withstand not only normal force levels encountered during simple up and down travel of the glazing panel, but also the aforesaid peak forces or loads encountered at initial start-up and travel stall. This adds considerably to the cost of window regulator assembly components. It would be desirable to reduce the peak forces encountered by certain window regulator assembly components, especially drive motors, to enable the use of less cosily, lighter service load components. In one known approach, so-called smart two-speed motors are employed which torque-up in stages, thereby reducing peak loads transmitted through the window regulator components. Unfortunately, multi-speed motors add to the cost and complexity of window regulator assemblies. Other known designs have contemplated the use of plastic stops to engage the sector gear or lifting arm, etc., at the full up or full down position. This approach fails to provide adequate drive force management and, in particular, fails to address the problem of start-up and travel stall other than at the full up and full down position.
An example of a window regulator employing a down-stop is shown in
U.S. Pat. No. 4,986,029 to Richter. A plastic spacer is provided in a window sash track between the rollers of a cross-arm regulator assembly shown in U.S. Pat. No. 4,924,627 to Lam et al. Compression, if any, of such plastic spacer would occur only at the full down position or full up position of the glazing panel.
It is an object of the present invention to provide window regulator assemblies in which drive force transmission through the assembly components is managed so as to reduce the peak forces experienced by at least some of the assembly components at start-up and travel stall at all points of travel of the glazing panel. Additional objects of the invention will be understood by those skilled in the art, that is, by those knowledgeable and experienced in this area of technology, in view of the following disclosure and detailed description of certain preferred embodiments.